PyPSA
Add support for using ParameterJuMP
ParameterJuMP allows defining variables as parameters and then compute dual values for them. Ie if one sets the capacity of a not-extendable generator or line as a parameter one can request the dual of the max generation constraint by querying the dual of the p_nom parameter.
Probably as simple as replacing all occurrences of JuMP.Model with JuMP.AbstractModel, as is already happening in the new moi branch by the introduction of the ModelView layers.
The question is: How would the user mark a data parameter as a ParameterJuMP-parameter? The parameter provision functions, i.e. get(::Element, ...) or get(::Data, ...), could maybe check whether something should be a parameter?